The research objective of this project is to investigate the interactions of adeno-associated virus with its host cell. The underlying hypothesis is that by understanding these interactions as they apply to the biology of the virus we can contribute to the use of AAV vectors for gene therapy. We focus on two areas of research; first is the characterization of two new AAV serotypes, AAV4 and AAV5. These new viral isolates are being studied both as natural mutations of other serotypes for understanding the biology of this genus of virus and as novel vectors for gene transfer. AAV4 and AAV5 each exhibit distinct mechanisms of cellular uptake compared with AAV2, and thus unique tissue tropisms. Our work has demonstrated improved transduction of airway lung cells and cell types within in the CNS. The second area of investigation addresses the mechanism by which the viral regulatory proteins alter the cellular environment in order to make it permissive for the viral life cycle. Current research has identified a number of cellular factors that interact with the viral regulatory proteins. The role of these proteins in the life cycle of the virus and their effect on cellular regulation are being investigated.